The present invention relates to closures for containers, such as bottle caps for closing bottle necks. The invention particularly relates to a liner disc held within a bottle cap outer shell which is sealingly pressed against a mouth forming part or xe2x80x9cfinishxe2x80x9d of the bottle neck, the cap outer shell having an inside thread engaged with an outside thread of the bottle neck. The liner disc includes a central downwardly domed portion with a liner seal layer applied to outside and underside surfaces of the liner disc. The central domed portion of the liner disc reacts to gas pressure held within the container to press the seal layer against an inside surface of the bottle finish to enhance the seal formed therewith.
In conventional bottle closures, a cap-shaped outer shell is threaded onto a bottle neck. A provision is made within the outer shell to seal the outer shell to the finish of the bottle neck. In some designs, such as disclosed in U.S. Pat. Nos. 4,658,976 and 5,356,021, the outer shell holds therein a liner disc which is held by the outer shell tightly against a top surface of the bottle finish.
Such closures for bottle necks are frequently employed to contain a gas pressurized liquid such as a carbonated soft drink. In the case of generally planar liner discs, experience has shown that pressure within the bottle can tend to bow the liner disc and an end wall of the outer shell outwardly, possibly opening the seal around the top surface of the bottle finish. Therefore, special designs and configurations must be employed to maintain the seal under such pressure.
It is also known to provide a liner disc within a bottle closure which has an outer shell with removable panels, removal of which creates evidence that the bottle closure has been previously unscrewed. Such an arrangement is disclosed for example in PCT published application WO94/29186, and U.S. Pat. No. 5,884,788, both hereby incorporated by reference. In this disclosed configuration, however, the liner disc is also a substantially planar member. Pressure from within the container would tend to oppose the sealing pressure of the liner disc against the bottle finish.
It would be desirable to provide a liner disc for a bottle closure which resists outward (upward) bowing under internal gas pressure, and which beneficially increases the sealing effect between the liner disc and the bottle finish due to the gas pressure.
The invention contemplates a closure cap for a bottle or other container which has a liner disc within a closure outer shell. The liner disc has a surrounding annular rim and a central, downwardly domed portion. The domed portion has an underside covered by a liner sealing material. The central domed portion of the liner disc extends in a direction into the bottle and provides increased resistance to upward doming of the liner disc under influence of internal bottle pressure. The domed central region provides an outward radial force under the influence of internal bottle pressure, to press the sealing material to an inside surface or finish of the bottle neck to enhance the sealing effect of the liner disc with the bottle neck.
Extending downwardly from the surrounding annular rim, the central domed portion is formed with an annular side wall and a contiguous convex bottom wall (convex downwardly). The annular side wall is coaxially arranged with the inside surface of the bottle neck. The annular side wall has an outside surface substantially parallel all around its circumference to an inside surface of the bottle neck.
Applied onto the convex bottom wall and onto the annular side wall is a layer of liner sealing material. Alternatively, the liner sealing material can be applied only on the annular side wall. The liner sealing material can be composed of a softer, or more resilient plastic material than the plastic of the liner disc for scaling the liner disc to the inside surface of the bottle neck.
When the closure is applied onto the bottle, the bottle neck fits between the closure outer shell and the annular side wall. The convex bottom wall fits inside the bottle neck and can radially expand under bottle pressure to press the annular side wall against an inside surface of the bottle neck. The liner sealing material on the annular side wall effects a seal between the annular side wall and the bottle neck.
The closure cap can include a tamper evidence system. The surrounding annular rim of the liner disc can include a formation thereon facing toward an end wall of the outer shell. The formation is configured to coact with tamper evidence panels on the end wall such that differential or relative rotation between the outer shell and the liner disc during closure removal causes breakage or separation of the tamper evidence panels on the outer shell. The breakage or separation of the tamper evidence panels gives the consumer a visual indication that the closure cap had been previously unscrewed or loosened from the bottle neck.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and embodiments thereof, from the claims, and from the accompanying drawings in which the details are fully and completely disclosed as part of the specification.